Bicycle rollers have been in use since the early 1900's. A bicycle roller is a dynamometer for bicycles that is powered by the bicycle rider. A bicycle roller is traditionally comprised of three rotatable cylinders positioned so that the rear wheel of the bicycle rides on two closely-spaced cylinders, and the front wheel of the bicycle rides on a third cylinder. In the typical application, the cylinder under the front wheel is coupled to one of the cylinders under the rear wheel by an elastic band such that the front cylinder is forced to rotate at approximately the same speed as the rear two cylinders. This allows the rider to control the bicycle, with steering enabled due to the rotation of the front wheel.
In the prior art, the amount of power, or wattage, that the bicyclist is required to exert to ride at a given speed on a bicycle roller was determined by the amount of rolling resistance resulting from tire distress as the tire rolls over each of the cylinders plus the wattage required to drive any external devices which exert resistance on one or more of the cylinders. Rolling resistance is predominantly a function of the cylinder diameter, tire pressure, and bicyclist weight. Relying on these factors alone provides a linear relationship of resistance versus speed. Simple devices that add a predictable amount of resistance such as the magnetic eddy-current device of U.S. Pat. No. 6,857,992 (incorporated herein by reference) can be added externally to the cylinders, but these are undesirable since they provide a linear speed-to-resistance relationship.
Prior art bicycle rollers have a linear relationship of speed versus resistance. This solution is unsatisfactory; when beginning to pedal the bike from rest on rollers, low resistance is desired to allow the wheels to accelerate quickly enough to enable sufficient steering dynamics to keep the bicycle stable on the rollers, however, to obtain a meaningful training session, a high amount of resistance is desired when pedaling at a rate suitable to achieve cardiovascular exercise benefit.
To achieve both objectives it is desired to have a “progressive” resistance relationship with speed. In other words, a non-linear relationship between speed and resistance where the slope of resistance versus speed increases with increasing speed is desired. This relationship is preferred because it mimics the non-linear effect of combined rolling resistance and wind resistance experienced when riding a bicycle in traditional fashion.
Stationary trainers that use devices external to the rollers, such as fluid resistance, friction, air-moving technologies or variable magnetic resistance devices (see U.S. Pat. No. 7,011,607, incorporated herein by reference) are designed to resemble realistic bicycle riding conditions. Each of these devices is external to the roller. Other than adding this type of device to a bicycle roller, and driving it through a power-transmission device, or through a complicated mechanical coupling to one of the driven cylinders, no attempt has been made to fully integrate progressive resistance technology within the drum of a bicycle roller so that external devices are not necessary. As such, an improved bicycle roller is desired.